We know that
<span>when a circle is divided into four equal parts, we will get 4 right angles
</span>so
360°/4=90° each part
see the attached figure to better understand the problem
If you divide a fraction by another fraction, this is equivalent to mupltiplying by its inverse:
so

divided by

is equivalent to

multiplied by by
which is

so the answer is

which is also 0.5
129 arrangements can be made 5 x 4 x 3 x 2 x 1= 120
slope = difference in y / difference in x
slope = 12 -11 / 2 -6
slope = 1 / -4
slope = -1 / 4 or
-.25